Coral reefs are the reason many people try diving. They are a source of income for tourism but also for local fisheries. They are home to a quarter of the ocean's fish. And they are under serious threat due to the third wave of coral bleaching.
Coral reefs are located all around the world's oceans from the tip of South Arica, to Australia, to Central America, Hawaii, Oceania and South Japan. Anyone who has seen the reefs - snorkelling or diving - will have been in awe of the colourful display of brightly shining animals. Having experienced their beauty it is even harder to grasp what it happening in our oceans at the moment; the equivalent above water would be a rainforest turning white.
Coral have algae living in their tissue which give corals their colour. They depend on each other but when the coral is under stress, they expel the algae, leaving them white and more sensible to disease.
What causes coral bleaching?
Coral turns white when it is stressed. This can be due to low tides, rising water temperature, overexposure to sunlight and pollution.Climate change is once more the source of the problem. If the global temperatures aren't rising as much as believed at first, it is because oceans are absorbing the heat. The waters are warming up.
This particular coral bleaching started in 2014, and has been predicted earlier this year due to the hot temperatures both on land and sea in 2015. The NOAA has projected that by the end of the year, 95 per cent of the coral reefs around the United States will have been affected by the causes of coral bleach. Oceans trap most of the heat from greenhouse gas emissions, but they also absorb about 25 per cent of the carbon dioxide we release into the air every year, increasing the water's acidity.
The most named cause for coral bleaching is El Niño, which is a prolonged warming of the Pacific usually lasting about three months. Occurring every four years, our oceans corals aren't threatened each time. It takes as extreme warming as well as the already rising ocean temperatures. Due to climate change, the frequency of the phenomenon seems to be increasing already.
"The baseline temperature has heated so much that reefs are no longer able to cope with what's normal in El Niño years," Richard Vevers, director of the XL Catlin Seaview Survey.
Why does it matter?
They are small organisms on the ocean bed, but they are much more important than they look. While they take up only 0.1 per cent of the ocean floor, they support a quarter of all marine species.Some resilient corals can withstand bleaching if they are healthy enough and will recover over time. Lately however, the bleaching seems to be repeated over a short period of time. While the first one was in 1998, followed by the second twelve years later, the coral only had about four years to try and recover this time. And due to other environmental threats such as overfishing and pollution, corals are not as healthy as they need to be to resist. Instead, they die and erode.
Corals are a habitat for fish and shellfish, extending the issue of coral bleaching to the wider marine life.
For locals, the loss of coral also means a loss of tourist income and higher vulnerability when storms come in. Incredible but true, the coral reefs around the world are assessed at about £6.1tn a year according to the Earth Index which values the services natural assets provide for people.
So yes, we should care that 4,600 square miles of corals are dying in our oceans and see it as yet another incentive to fight climate change.
By Claire Herbaux - Online Journalism Intern
Find out more about how coral bleaching is affecting Belize.
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